SPACE/COSMOS
Astronomers surprised by mysterious shock wave around dead star
ESO
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The central square image, taken with the MUSE instrument on ESO’s Very Large Telescope, shows shock waves around the dead star RXJ0528+2838. When a star moves through space it can push away nearby material creating a so-called bow shock, which in this image is glowing in red, green and blue. The colours represent hydrogen, nitrogen and oxygen, respectively. These shocks are usually produced by a strong outflow expelled from the star. However, in the case of RXJ0528+2838 –– a white dwarf with a Sun-like companion –– astronomers discovered that the shock wave can’t be explained by any known mechanism. Some hidden energy source, perhaps magnetic fields, could be the answer to this mystery.
view moreCredit: ESO/K. Ilkiewicz and S. Scaringi et al. Background: PanSTARRS
Gas and dust flowing from stars can, under the right conditions, clash with a star’s surroundings and create a shock wave. Now, astronomers using the European Southern Observatory’s Very Large Telescope (ESO’s VLT) have imaged a beautiful shock wave around a dead star — a discovery that has left them puzzled. According to all known mechanisms, the small, dead star RXJ0528+2838 should not have such structure around it. This discovery, as enigmatic as it’s stunning, challenges our understanding of how dead stars interact with their surroundings.
“We found something never seen before and, more importantly, entirely unexpected,” says Simone Scaringi, associate professor at Durham University, UK and co-lead author of the study published today in Nature Astronomy. “Our observations reveal a powerful outflow that, according to our current understanding, shouldn’t be there,” says Krystian Ilkiewicz, a postdoctoral researcher at the Nicolaus Copernicus Astronomical Center in Warsaw, Poland and study co-lead. ‘Outflow’ is the term used by astronomers to describe the material that is ejected from celestial objects.
The star RXJ0528+2838 is located 730 light-years away and, like the Sun and other stars, it rotates around our galaxy’s centre. As it moves, it interacts with the gas that permeates the space between stars, creating a type of shock wave called a bow shock, “a curved arc of material, similar to the wave that builds up in front of a ship,” explains Noel Castro Segura, research fellow at the University of Warwick in the UK and collaborator in this study. These bow shocks are usually created by material outflowing from the central star, but in the case of RXJ0528+2838, none of the known mechanisms can fully explain the observations.
RXJ0528+2838 is a white dwarf — the left-over core of a dying low-mass star — and has a Sun-like companion orbiting it. In such binary systems, the material from the companion star is transferred to the white dwarf, often forming a disc around it. While the disc fuels the dead star, some of the material also gets ejected into space, creating powerful outflows. But RXJ0528+2838 shows no signs of a disc, making the origin of the outflow and resulting nebula around the star a mystery.
“The surprise that a supposedly quiet, discless system could drive such a spectacular nebula was one of those rare ‘wow’ moments,” says Scaringi.
The team first spotted a strange nebulosity around RXJ0528+2838 on images from the Isaac Newton Telescope in Spain. Noticing its unusual shape, they observed it in more detail with the MUSE instrument on ESO’s VLT. “Observations with the ESO MUSE instrument allowed us to map the bow shock in detail and analyse its composition. This was crucial to confirm that the structure really originates from the binary system and not from an unrelated nebula or interstellar cloud,” Ilkiewicz explains.
The shape and size of the bow shock imply that the white dwarf has been expelling a powerful outflow for at least 1000 years. Scientists don’t know exactly how a dead star without a disc can power such a long-lasting outflow — but they do have a guess.
This white dwarf is known to host a strong magnetic field, which has been confirmed by the MUSE data. This field channels the material stolen from the companion star directly onto the white dwarf, without forming a disc around it. “Our finding shows that even without a disc, these systems can drive powerful outflows, revealing a mechanism we do not yet understand. This discovery challenges the standard picture of how matter moves and interacts in these extreme binary systems,” Ilkiewicz explains.
The results hint at a hidden energy source, likely the strong magnetic field, but this ‘mystery engine’, as Scaringi puts it, still needs to be investigated. The data show that the current magnetic field is only strong enough to power a bow shock lasting for a few hundred years, so it only partly explains what the astronomers are seeing.
To better understand the nature of such discless outflows, many more binary systems need to be studied. ESO’s upcoming Extremely Large Telescope (ELT) will help astronomers “to map more of these systems as well as fainter ones and detect similar systems in detail, ultimately helping in understanding the mysterious energy source that remains unexplained,” as Scaringi foresees.
More information
This research was presented in a paper titled “A persistent bow shock in a diskless magnetised accreting white dwarf” to appear in Nature Astronomy (doi: 10.1038/s41550-025-02748-8).
The team is composed of Krystian Ilkiewicz (Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Warsaw, Poland and Centre for Extragalactic Astronomy, Department of Physics, Durham University, Durham, UK [CEA Durham]), Simone Scaringi (CEA Durham and INAF-Osservatorio Astronomico di Capodimonte, Naples, Italy [Capodimonte]), Domitilla de Martino (Capodimonte), Christian Knigge (Department of Physics & Astronomy, University of Southampton, Southampton, UK), Sara E. Motta (Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Brera, Merate, Italy and University of Oxford, Department of Physics, Oxford, UK [Oxford]), Nanda Rea (Institute of Space Sciences (ICE, CSIC), Barcelona, Spain and Institut d’Estudis Espacials de Catalunya (IEEC), Castelldefels, Spain), David Buckley (South African Astronomical Observatory, South Africa [SAAO] and Department of Astronomy & IDIA, University of Cape Town, Rondebosh, South Africa [Cape Town] and Department of Physics, University of the Free State, Bloemfontein, South Africa), Noel Castro Segura (Department of Physics, University of Warwick, Coventry, UK), Paul J. Groot (SAAO and Cape Town and Department of Astrophysics/IMAPP, Radboud University, Nijmegen, The Netherlands), Anna F. McLeod (CEA Durham and Institute for Computational Cosmology, Department of Physics, University of Durham, Durham UK), Luke T. Parker (Oxford), and Martina Veresvarska (CEA Durham).
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Journal
Nature Astronomy
Article Title
A persistent bow shock in a diskless magnetised accreting white dwarf
‘Death by a thousand cuts’: Young galaxy ran out of fuel as black hole choked off supplies
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Astronomers have spotted one of the oldest ‘dead’ galaxies yet identified, and found that a growing supermassive black hole can slowly starve a galaxy rather than tear it apart.
The researchers, led by the University of Cambridge, used data from the James Webb Space Telescope and the Atacama Large Millimeter Array (ALMA), to study a galaxy in the early universe – about three billion years after the Big Bang.
The galaxy, called GS-10578 but nicknamed ‘Pablo’s Galaxy’ after the astronomer who first observed it in detail, is massive for such an early period in the universe: about 200 billion times the mass of our Sun, and most of its stars formed between 12.5 and 11.5 billion years ago.
view moreCredit: JADES Collaboration
Astronomers have spotted one of the oldest ‘dead’ galaxies yet identified, and found that a growing supermassive black hole can slowly starve a galaxy rather than tear it apart.
The researchers, led by the University of Cambridge, used data from the James Webb Space Telescope and the Atacama Large Millimeter Array (ALMA), to study a galaxy in the early universe – about three billion years after the Big Bang.
The galaxy, called GS-10578 but nicknamed ‘Pablo’s Galaxy’ after the astronomer who first observed it in detail, is massive for such an early period in the universe: about 200 billion times the mass of our Sun, and most of its stars formed between 12.5 and 11.5 billion years ago.
Pablo’s Galaxy appears to have ‘lived fast and died young’: it stopped forming new stars, despite its relatively young age, due to an almost total absence of the cold gas stars need to form.
The supermassive black hole at the galaxy’s centre appears to be the culprit. But instead of a single cataclysmic event, the galaxy suffered ‘death by a thousand cuts’ as the black hole repeatedly heated the gas in and around the galaxy, preventing it from resupplying the galaxy with fresh gas and slowly strangling star formation. The results are reported in the journal Nature Astronomy.
The researchers spent nearly seven hours observing the galaxy with ALMA, hoping to detect carbon monoxide – a tracer of cold hydrogen gas. Instead, they found nothing.
“What surprised us was how much you can learn by not seeing something,” said co-first author Dr Jan Scholtz from Cambridge’s Cavendish Laboratory and Kavli Institute for Cosmology. “Even with one of ALMA’s deepest observations of this kind of galaxy, there was essentially no cold gas left. It points to a slow starvation rather than a single dramatic death blow.”
Meanwhile, JWST spectroscopy revealed powerful winds of neutral gas streaming out of the galaxy’s supermassive black hole at 400 kilometres per second, removing 60 solar masses of gas every year. Those numbers suggest the galaxy’s remaining fuel was depleted in as little as 16 to 220 million years – far faster than the billion-year timescale typical for similar galaxies.
“The galaxy looks like a calm, rotating disc,” said co-first author Dr Francesco D’Eugenio, who is also affiliated with the Kavli Institute for Cosmology. “That tells us it didn’t suffer a major, disruptive merger with another galaxy. Yet it stopped forming stars 400 million years ago, while the black hole is yet again active. So the current black hole activity and the outburst of gas we observed didn’t cause the shutdown; instead, repeated episodes likely kept the fuel from coming back.”
By reconstructing the galaxy’s star-formation history, the researchers concluded that the galaxy evolved with net-zero inflow – meaning fresh gas never refilled its tank. Rather than blowing away all its gas in one go, the black hole seems to have heated or expelled incoming material over multiple cycles, preventing the galaxy from replenishing itself.
“You don’t need a single cataclysm to stop a galaxy forming stars, just keep the fresh fuel from coming in,” said Scholtz.
The findings help explain a growing population of massive, surprisingly old-looking galaxies seen by Webb in the early Universe. “Before Webb, these were unheard of,” said Scholtz. “Now we know they’re more common than we thought – and this starvation effect may be why they live fast and die young.”
The study shows the advantages of combining ALMA’s ultra-deep radio observations with JWST’s infrared spectra. Future work will target more galaxies like this one to see whether slow starvation, rather than violent blowouts, is the norm for galaxies in the early universe.
The Cambridge team was awarded additional 6.5 hours of JWST time using the MIRI instrument. These new observations targeting the warmer hydrogen gas will tell us more about the exact mechanisms that this supermassive black hole is using to stop the galaxy from forming stars.
The research was supported in part by the European Union, the European Research Council, the Royal Society and the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).
ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSTC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The James Webb Space Telescope is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).
Journal
Nature Astronomy
Article Title
Measurement of the gas consumption history of a massive quiescent galaxy
Article Publication Date
12-Jan-2026
Key to researching large planets: Research team discovers novel form of water
Joint press release from the University of Rostock, CNRS-École polytechnique, and Helmholtz-Zentrum Dresden-Rossendorf
University of Rostock
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Schematic representation of the microscopic structure of superionic water, in which the oxygen atoms form a solid crystal lattice, while hydrogen ions are virtually free to move within it. With the aid of powerful lasers, this extreme state, which otherwise only occurs inside large planets, could be measured experimentally.
view moreCredit: (Image: Greg Stewart / SLAC National Accelerator Laboratory)
Temperatures of several thousand degrees Celsius and pressures of millions of atmospheres: superionic water only forms under extreme conditions. These conditions transform water into an unusual state in which hydrogen ions move freely through a solid lattice of oxygen atoms.
Milestone in planetary research
Since this so-called phase conducts electrical current particularly well, it is associated with the formation of the unusual magnetic fields of ice giants. Due to the large amounts of water inside Uranus and Neptune, superionic water could even be the most common form of water in our solar system.
New study reveals complex details about water
Although superionic water has already been produced in previous experiments, its detailed structure remained unclear until now. Previous studies suggested that the oxygen atoms in superionic ice arrange themselves in either a body-centered cubic or a face-centered cubic structure, i.e., in two variants of a cube lattice: in the former, an additional atom sits in the center of the cube, in the latter, on each cube face.
However, the new study paints a much more complex picture. The researchers found that superionic water forms a structure that combines both face-centered cubic and hexagonal close-packed stacking. The latter corresponds to a layering of closely packed atoms in hexagonal patterns and, together with the cubic areas, leads to significant stacking errors. Instead of arranging themselves in a single regular configuration, the oxygen atoms form a hybrid, misstructured sequence – a pattern that can only be made visible by high-precision measurements using state-of-the-art X-ray lasers.
Researchers create extreme conditions
To gain these insights, the team conducted two experiments: one on the Matter in Extreme Conditions (MEC) instrument at LCLS in the US and another on the HED-HIBEF instrument at European XFEL. These facilities enable researchers to compress water to pressures of more than 1.5 million atmospheres and heat it to temperatures of several thousand degrees Celsius – while simultaneously recording its atomic structure within trillionths of a second.
Insight into the structure of water creates new possibilities
The results, which are consistent with the most advanced simulations, show that superionic water can exhibit structural diversity similar to that of solid ice, which forms a variety of different crystal structures depending on pressure and temperature. The work underscores that water—despite its apparent simplicity—continually reveals new and remarkable properties under extreme conditions. In addition, the findings provide valuable constraints for improved models of the interiors and evolution of ice giants, which are also very common outside our solar system.
The project was supported as part of a joint initiative between the German Research Foundation (DFG) and the French research funding agency ANR. More than 60 scientists from Europe and the US were involved in the experiments and evaluation.
Journal
Nature Communications
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Observation of a mixed close-packed structure in superionic water
